[cardcounter0]

Exact advantage would require the exact set of rules, the count system being used, the amount of penetration, and how much of the deck remains at that point.

A rough rule of thumb is you gain .5% for every +1 increase in the HiLo count minus the house edge. So at a true count of +1 you usually have a slight advantage, at a true count of +2, an advantage a little over .5%, etc.